1. Field of the Invention
The invention relates to an illuminating device, more particularly to an organic light emitting diode illuminating device.
2. Description of the Related Art
Referring to FIG. 1, a conventional organic light emitting diode (abbreviated as OLED hereinafter) illuminating device 1 is shown to include a transparent substrate 11, an anode layer 12 (such as an ITO transparent conductive layer) formed on the transparent substrate 11, an organic light emitting structure 13, and a cathode layer 14 formed on the organic light emitting structure 13.
The organic light emitting structure 13 includes a hole injection layer 131, a first hole transfer layer 132, a blue light emitting layer 133 that is made of a blue light emitting material, a first electron transfer layer 134, a charge generation layer 135, a second hole transfer layer 136, a yellow light emitting layer 137 that is made of a yellow light emitting material, a second electron transfer layer 138, and an electron injection layer 139 which are stacked sequentially along a direction P as shown in FIG. 1.
The conventional OLED illuminating device 1 generates white light by mixing the generated blue light from the blue light emitting layer 133 with the generated yellow light from the yellow light emitting layer 137. However, the total thickness of the conventional OLED illuminating device 1, which is composed of at least 11 layers, is relatively large and results in a low production yield, which increases the production cost. Moreover, the blue light emitting material of the blue light emitting layer 133 has shorter life compared to the yellow light emitting material of the yellow light emitting layer 137, thereby generating chromatic shift problems of the conventional OLED illuminating device after being in use for a long period of time. Furthermore, chrominance of the illuminated light of the conventional OLED illuminating device 1 is determined by the blue and yellow light emitting materials which are adopted in the respective blue and yellow light emitting layers 133 and 137. Therefore, once the blue and yellow light emitting materials are chosen, chrominance of the illuminated light of the conventional OLED illuminating device 1 is then determined and cannot be adjusted.